package com.homework;

import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.NullWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Mapper;

import java.io.IOException;

public class SortMapper extends Mapper<LongWritable, Text, LongWritable, NullWritable> {

    LongWritable outKey = new LongWritable();
    NullWritable outValue = NullWritable.get();

    /**
     * 按行处理数据源
     * 一行是数字，在mapper的过程中把Text类型的输入数据转换为LongWritable作为mapper的输出key,
     * 借助shuffle过程中的默认自动排序来实现需求中的数据整体排序
     * @param key
     * @param value
     * @param context
     * @throws IOException
     * @throws InterruptedException
     */
    @Override
    protected void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException {
        long res =  Long.parseLong(value.toString());
        outKey.set(res);
        context.write(outKey, outValue);
    }
}